1. Technical Field
The present invention relates to a piezoelectric element drive circuit and various apparatuses such as a robot including a piezoelectric element drive circuit.
2. Related Art
In the related art, a piezoelectric actuator (piezoelectric drive device) using a piezoelectric element is known (for example, JP-A-2004-320979). According to a basic configuration of the piezoelectric drive device, four piezoelectric elements are configured to be arranged in two rows and two columns on two surfaces of a reinforcing plate. Eight piezoelectric elements in total are disposed on both sides of the reinforcing plate. Each of the piezoelectric elements is a unit which interposes each piezoelectric substance between two electrodes. The reinforcing plate is used as one electrode of the piezoelectric element. One end of the reinforcing plate has a protrusion portion disposed in order to rotate a rotor by coming into contact with the rotor serving as a driven body. If an AC voltage is applied to the two piezoelectric elements arranged at opposite angles among the four piezoelectric elements, the two piezoelectric elements perform expansion and contraction movement. In response to the movement, the protrusion portion of the reinforcing plate performs reciprocating movement or elliptical movement. Then, in response to the reciprocating movement or the elliptical movement of the protrusion portion of the reinforcing plate, the rotor serving as the driven body is rotated in a predetermined rotation direction. The rotor can be rotated in the opposite direction by switching from the two piezoelectric elements to which the AC voltage is applied to the other two piezoelectric elements.
In the related art, as the piezoelectric substance used for the piezoelectric drive device, a so-called bulky piezoelectric substance is used. The “bulky piezoelectric substance” described herein means a piezoelectric substance whose thickness is 100 μm or greater. The reason of using the bulky piezoelectric substance is to increase the thickness of the piezoelectric substance in order to sufficiently strengthen force applied from the piezoelectric drive device.
In addition, in the piezoelectric drive device which employs the piezoelectric element, a technology is known in which an inductive element is connected to the piezoelectric element in parallel in order to decrease power consumption (refer to JP-A-7-231683).
Incidentally, there is a need to miniaturize a piezoelectric drive device and to use the miniaturized piezoelectric drive device as a small actuator which can be accommodated in a small space. However, in a case of the actuator which employs the piezoelectric element formed of a thin film in which a thickness of the piezoelectric substance is smaller than 100 μm, a large amount of currents flows due to a large electrostatic capacity of the piezoelectric element, thereby causing a problem in that current consumption cannot be sufficiently decreased in the related art.